inline4 Posted February 3, 2011 Report Share Posted February 3, 2011 3.7 or 3.9 ? would it be a negligible difference? Quote Link to comment
ggzilla Posted February 3, 2011 Report Share Posted February 3, 2011 3.9 will accelerate faster ... with any engine Quote Link to comment
DISLEXICDIME Posted February 3, 2011 Report Share Posted February 3, 2011 411's Quote Link to comment
inline4 Posted February 3, 2011 Author Report Share Posted February 3, 2011 3.9 will accelerate faster ... with any engine why did the roadster have a 3.90 in the 1600 and a 3.7 with the 2000, because of the smaller size 1.6L? Quote Link to comment
ggzilla Posted February 3, 2011 Report Share Posted February 3, 2011 They fitted the 3.70 for improved fuel economy. If that is your goal, the 3.7 is "better". Quote Link to comment
Laecaon Posted February 3, 2011 Report Share Posted February 3, 2011 why did the roadster have a 3.90 in the 1600 and a 3.7 with the 2000, because of the smaller size 1.6L? Well doesnt the L16 rev higher than the L20b? so higher rev takes car of lower gearing, Engine not as torqy. L20b definitely has more torque and therefor can take the lower gearing. I imagine this might be true with the R16/R20. Quote Link to comment
ggzilla Posted February 3, 2011 Report Share Posted February 3, 2011 Naw, it has nothing to do with the rev limit. The H20 can take lower gearing -- it can rev just as high as the R16. But you are right in that the less-performance gearing (3.7) won't be as bad with the larger engine. Quote Link to comment
HRH Posted February 3, 2011 Report Share Posted February 3, 2011 Massive hp works better with super high gears. Basically the higher the gear ratio, the less torque multiplication you have, the higher theoretical top speed, and the best mileage to the point of diminishing return. Lower gears are better for climbing, acceleration, and power out of low hp motors. For instance, I'm running 4.11s in the 510 right now. Combined with the L20 and the goofy shift (close ratio) 5 speed, the 510 rips up, but also has an rpm limited redline of 120. That's at 6500 rpm in 5th gear. That means I'm turning 3500 in 5th at 60 mph on the freeway. Not exactly ideal. But I want my acceleration factor, so I deal with it. The KA probably has enough hp to push 3.7s just fine, however, with the KA trans, you'll be really tall geared. Think pulling 1500 rpm in 5th on the freeway, yet not having enough power to push into the 140 mph range because it's just not enough power. I ran the stock 3.7 Subi diff rear end in the 510 for a while. It was definitely high geared, and I couldn't even come close to redlining in 5th. It moved the theoretical top speed much higher, but not enough oomph to get there. I'd go with the 3.9s. Still good economy, but also good power. Quote Link to comment
Z-train Posted February 3, 2011 Report Share Posted February 3, 2011 Here ya go: http://www.wallaceracing.com/calcmph.php Quote Link to comment
sinner720st Posted February 3, 2011 Report Share Posted February 3, 2011 neat calculator (just realized im future screwed, pathy rear with 4.60's will not be cool) Quote Link to comment
kmc63 Posted February 3, 2011 Report Share Posted February 3, 2011 3.7 or 3.9 ? would it be a negligible difference? My 510 has the vg six cylinder. It still has the stock 3.90 rear end,first gear is useless its like a compound low in an old pickup.I just picked up a 3.70 lsd I think it will make a difference atleast a little. Quote Link to comment
inline4 Posted February 3, 2011 Author Report Share Posted February 3, 2011 so should I just keep the 3.9 rear end instead of swapping the 200 3.7 rear end if I'm throwing a KA into a roadster? Quote Link to comment
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